This invention relates to scroll fluid apparatus, and more particularly it is concerned with a construction of the scroll fluid apparatus suitable for discharging a lubricant collecting at an outer peripheral portion of an end plate of an orbiting scroll member to reduce a drive force required to operate the apparatus.
In, for example, Japanese Laid Open Pat. No. 73886/82 a sealed type electric compressor in the form of a scroll fluid apparatus is proposed which comprises a compressor section and an electric motor section contained in a sealed container, and a fluid passage extending through a wall of the sealed container and connected through a line to outside equipment which may be an evaporator or condenser of a refrigerating apparatus. The scroll type compressor section comprises a fixed scroll member and an orbiting scroll member in meshing engagement with each other which constitute the essential portions of the compressor. The fixed scroll member and orbiting scroll member each includes an end plate, and a wrap of vortical form located in upright position on the each end plate and having an involute curve or a curve similar to that. A suction port for a fluid is formed in a position in the vicinity of an outer side of a space defined between the two scroll members, and a discharge port opens in a position close to the center of the fixed scroll member. A rotation preventing member in the form of an Oldham's ring is mounted between the orbiting scroll member and a frame or the fixed scroll member to prevent the orbiting scroll member from rotating on its own axis, and a crankshaft is kept in engagement with the orbiting scroll member through a bearing to move the orbiting scroll member in orbiting movement about the center of the fixed scroll member without rotating on its own axis, so as to compress a fluid in the sealed space defined between the two scroll members and discharge the compressed fluid through the discharge port. To compress the fluid and discharge the compressed fluid efficiently as described hereinabove, it is necessary that the orbiting scroll member be forced against the fixed scroll member with a suitable force. The axial biasing force which urges the orbiting scroll member against the fixed scroll member is obtained by the difference between the pressure in compression chambers and the pressure applied to the back of the orbiting scroll member, and the difference in pressure is introduced through a fine communicating port communicating the compression chambers with the back of the orbiting scroll member.
Meanwhile, a lubricant collecting in the sealed container is utilized for cooling the bearings and sliding portions of the compressor section. The lubricant is fed to each bearing through oil ducts formed in the crankshaft by the difference in pressure between an intermediate pressure and a high pressure, and then flows into a back pressure chamber on the back of the orbiting scroll member. The lubricant flowing into the back pressure chamber is discharged therefrom in suitable amount into the compression chambers through the communicating port during operation and entrained in the compressed gas to flow in circulation therewith.
In the scroll fluid apparatus of the aforesaid construction, the lubricant flowing into the back pressure chamber is discharged into the compression chambers through the communicating port formed in the end plate of the orbiting scroll member. However, if the amount of the lubricant fed to the bearings exceeds the discharge capacity of the communicating port, then the back pressure chamber would be filled with the lubricant which would be agitated by a balance weight, causing a loss of power. The lubricant would invade a clearance in an outer peripheral portion of the end plate of the orbiting scroll member, and if such clearance were filled with the lubricant, the lubricant would be compressed by the orbiting movement of the orbiting scroll member, thereby causing an increase in the power necessary for operating the apparatus.